This invention relates generally to a logic-controlled explosive igniter, and more particularly to a semiconductor bridge igniter mounted on the same semiconductor die as its triggering switch.
A new igniter of a semiconductor nature which is especially useful in conjunction with insensitive high explosives and pyrotechnics is the semiconductor bridge ignitor (SCB) disclosed in U.S. Patent No. 4,708,060 of Robert Bickes, et al. As disclosed therein, an SCB is an electrical material (typcially, a highly doped semiconductor) formed as a bridge of small size (e.g. 100 um long x 400 um wide), having a resistance on the order of one ohm, extending between two spaced conductive pads. Application of a relatively low power pulse (e.g. 15 us, 25 A, 3 mJ) across the bridge causes the bridge to burst, igniting an explosive charge placed against the bridge. The device may typically be packaged in a small container with the electrical leads at one end and the explosive at the other end. The particular advantages of the SCB include ease of manufacture, repeatability of fire characteristics, and safety. Further details may be found in the aforementioned patent, the disclosure of which patent is incorporated herein by reference.
A prior art detonator cap is shown in U.S. Pat. No. 4,145,970 of J. Hedberg et al., Mar. 27, 1979. This patent discloses a cylindrical case having an explosive charge at one end thereof, an electrically initiated device adjacent the explosive charge, and a control circuit comprising a capacitor that is charged through a first relay upon receipt of a first signal, and a delay circuit that closes a second relay to discharge the capacitor to fire the device after a predetermined delay. An isolating transformed is used for frequency tuning and isolating the applied voltage.
By nature, a detonating device is only used once. Accordingly, it is highly desirable to minimize the cost of each detonator. The device of Hedberg requires a plurality of electrical connections between discrete electronic components, a labor-intensive construction.